More Detailed Version:
As I understand it:
To your first question: Yes and no. The 6th Circuit found Michigan’s registry scheme to be punitive in effect. In the context of that lawsuit, it means that the statute violates Ex Post Facto protection, and that registry requirements cannot be applied retroactively: Registrants are only bound by registry requirements and limitations that were in effect when their crime was committed.
This ruling doesn’t automatically apply to any other state besides Michigan. Registered citizens that live in states within the 6th circuit could sue and the 6th Circuit should be bound by its own precedent. Residents in within other circuits could sue (as NCRSOL has in NC) and attempt to use the 6th Circuit’s ruling to bolster their case but the 6th Circuit ruling is not binding in other circuits.
As to your second question: Yes, the Supreme Court could agree with the 6th Circuit. (Let’s all just assume that they will grant review.) If SCOTUS upholds the ruling below (the 6th Circuit ruling) then that means that they feel Michigan’s SOR scheme is punitive in effect and can’t be applied retroactively. This is the desired outcome because if the registry is ruled punitive, then the next obvious step is to challenge all registry requirements as “Cruel and Unusual Punishment.” The fact that it is unusual is easily argued, since no other major class of ex-offender is targeted the way “sex offenders” are. So then the question becomes, “Is it cruel?” I’d say yes, as would most of us. This is where studies of collateral consequences are worth their weight in gold.
The other alternative is that SCOTUS overturns the 6th Circuit ruling. This would essentially invalidate any and all claims of punitiveness in regards to registries. Our only hope of ending the registries at that point is to lobby with legislators at the state and federal levels for change.